Quickstart

This quickstart walks through the two layers. Start with the core layer (pure strings, works anywhere), then move to the file layer (real files, Node.js/Electron).

Prerequisite: install the package first.

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1. Core layer — patch a string in the browser

Import from @powerduck/conf-patch/core. No filesystem is touched; you get the new content back as a string and store it wherever you like (localStorage, IndexedDB, a string constant).

import {
  patchContent,
  setContentValue,
  deleteContentValue,
} from "@powerduck/conf-patch/core";

// --- JSON: apply multiple RFC 6902 operations ---
const json = JSON.stringify({ name: "my-app", version: "1.0.0" }, null, 2);

const updatedJson = patchContent(
  json,
  [
    { op: "add", path: ["description"], value: "My awesome application" },
    { op: "replace", path: ["version"], value: "1.1.0" },
  ],
  "json",
);

console.log(updatedJson);
// {
//   "name": "my-app",
//   "version": "1.1.0",
//   "description": "My awesome application"
// }

// Store it however you like — no fs required.
localStorage.setItem("config", updatedJson);

Same idea with YAML

import { setContentValue, deleteContentValue } from "@powerduck/conf-patch/core";

// Set a nested value in YAML (the "server" parent already exists).
const yaml = "name: my-app\nserver:\n  host: localhost\n";

const updatedYaml = setContentValue(yaml, ["server", "port"], 8080, "yaml");
console.log(updatedYaml);
// name: my-app
// server:
//   host: localhost
//   port: 8080

// Delete a value.
const cleaned = deleteContentValue(updatedYaml, ["server", "host"], "yaml");

note

setContentValue uses the add operation, which adds or replaces an existing object property. deleteContentValue uses remove. See patchContent for the full operation set.

---

2. File layer — patch a file on disk

Import from the main entry. These functions are async, read/write real files, and use atomic writes with locking.

import { setConfigValue, readConfigFile, patchConfigFile } from "@powerduck/conf-patch";

// Set a nested value in a YAML file (atomic, lock-guarded).
await setConfigValue("config.yaml", ["database", "port"], 5432);

// Read the file back.
const content = await readConfigFile("config.yaml");
console.log(content);

// Apply several operations to a JSON file in one locked transaction.
await patchConfigFile("config.json", [
  { op: "replace", path: ["server", "host"], value: "0.0.0.0" },
  { op: "add", path: ["server", "ssl"], value: true },
  { op: "remove", path: ["legacySection"] },
]);

The format is auto-detected from the file extension (.json, .jsonc, .yaml, .yml). Pass format explicitly when the extension is ambiguous.

---

3. Error handling

Both layers throw on invalid input. In strict mode (the default) a failed patch operation also throws.

import { patchContent } from "@powerduck/conf-patch/core";

try {
  // "remove" requires the path to exist.
  patchContent('{"name": "app"}', [{ op: "remove", path: ["missing"] }], "json");
} catch (error) {
  // Error: [confedit] Cannot remove a value that does not exist at path: ["missing"]
  console.error(error instanceof Error ? error.message : error);
}

Set strict: false to skip failing operations instead of throwing:

patchContent(
  '{"name": "app"}',
  [{ op: "remove", path: ["missing"] }],
  "json",
  { strict: false }, // logs a warning, returns the original content
);

---

4. Electron IPC example

A common pattern is to run the file layer in the Electron main process and expose it over IPC:

// Electron main process (CommonJS)
const { setConfigValue, readConfigFile } = require("@powerduck/conf-patch");

ipcMain.handle("config:set", async (_event, { filePath, path, value }) => {
  try {
    await setConfigValue(filePath, path, value);
    return { success: true };
  } catch (error) {
    return { success: false, error: error.message };
  }
});

ipcMain.handle("config:read", async (_event, { filePath }) => {
  try {
    const data = await readConfigFile(filePath);
    return { success: true, data };
  } catch (error) {
    return { success: false, error: error.message };
  }
});

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Next steps

• API reference — every function, type, and option.
• Examples — JSON patching, YAML, JSONC with comments, OpenAPI validation, and file locking.